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Biomedical subjects

A Baird

Publications and source records attributed to A Baird.

At least 91 records · Page 5Linked to original sources
PubMed1994

Fibroblast growth factors: activities and significance of non-neurotrophin neurotrophic growth factors.

Although first characterized by virtue of their ability to stimulate endothelial cell proliferation in vitro and angiogenesis in vivo, the fibroblast growth factors are now also well recognized for their neurotrophic activities. Understanding the physiological significance of these multifunctional, virtually ubiquitous and pluripotential molecules, however, remains enigmatic. Recent advances describing their molecular, biochemical and biological characteristics has led to a better understanding of their role in the central nervous system.

Animals↗
PubMed1994

Fibroblast growth factor in the hypothalamic-pituitary axis: differential expression of fibroblast growth factor-2 and a high affinity receptor.

In situ hybridization and immunohistochemistry were used to map gene expression and protein distribution of basic fibroblast growth factor (FGF-2) in the hypothalamic-pituitary system. Although the expression of FGF-2 mRNA in the pituitary is low, the protein is widely distributed in both its neural and anterior lobes. In the anterior lobe, immunoreactive (ir-) FGF-2 localizes to basement membranes and select endocrine cells. In the neural lobe, ir-FGF-2 is detected in basement membranes, pituicytes, and Herring bodies. Analyses of FGF high affinity receptor (FGFR) immunoreactivity in the anterior pituitary establishes a distribution of FGFR similar to that of FGF-2. In the neural lobe, ir-FGFR is associated with nerve fibers, pituicytes, and Herring bodies. Unlike FGF-2, the distribution of FGFR1 mRNA correlates well with the presence of the immunoreactive receptor. In the hypothalamus, magnocellular neurons of paraventricular and supraoptic nuclei contain ir-FGF-2 and ir-FGFR. In the median eminence, ir-FGF-2 and ir-FGFR is associated with fibers, glial, and endothelial cells. Ependymal and subependymal cells lining the third ventricle also show high levels of ir-FGF-2 and ir-FGFR and mRNAs. Overall, there is a specific and selective distribution of FGF-2 and its high affinity receptor(s) in the hypothalamo-pituitary axis. This localization lead us to postulate a role in neurohypophyseal functions, possibly water balance.

Animals↗
PubMed1994

Coordinated pattern of expression and localization of insulin-like growth factor-II (IGF-II) and IGF-binding protein-2 in the adult rat brain.

Insulin-like growth factors (IGFs) have numerous actions on neuronal and glial cell function in vitro, although their in vivo roles within the central nervous system (CNS) remain undefined. Levels of IGF-II are high in most rat tissues before the third postnatal week, but rapidly decrease thereafter, except in the brain and spinal cord, where elevated titers are present in the adult. This suggests a function of IGF-II within the CNS. IGF-binding proteins (IGFBPs) modify the type 1 IGF receptor-mediated activity of IGFs, thereby regulating the activities of IGF-II in the CNS. In this study, we use a ribonuclease protection assay, in situ hybridization, and immunohistochemistry to demonstrate that IGF-II and one of the major CNS binding proteins, IGFBP-2, show a striking congruency in their anatomical pattern of expression and localization throughout the adult rat brain. Both proteins are synthesized predominantly in the leptomeninges, choroid plexus, and parenchymal microvasculature, but become localized, remote from the site of synthesis, in the myelin sheaths of individual myelinated axons and in all of the myelinated nerve tracts in the brain, which presumably represents the site of IGF-II bioactivity. The spatial disparity between sites of synthesis and sites of bioactivity suggests a key role for IGFBP-2 in the regulation of IGF-II bioavailability within the brain.

Animals↗
PubMed1994

Acidic and basic FGF mRNA expression in the middle ear mucosa during experimental acute and chronic otitis media.

Fibroblast growth factors (FGFs) induce the proliferation and differentiation of cells of mesodermal and neuroectodermal origin. Using in situ hybridization, messenger ribonucleic acid encoding acidic FGF, basic FGF and FGF receptor 1 (FGFR1) were localized in the middle ear mucosa of experimental animals with acute and chronic immune-mediated otitis media with effusion (OME). Basic FGF-labeled cells were seen in the subepithelial connective tissue layer (SE) preferentially near the epithelial basement membrane. Acidic FGF-labeled cells were seen in the SE, preferentially near blood vessels and occasionally in the cellular middle ear effusion (CE). FGFR1-labeled cells were seen in the SE and in the CE. The distribution of labeled cells in the middle ear suggests that basic FGF is produced by fibroblasts, acidic FGF is produced by leukocytes, and FGFR1 is produced by both fibroblasts and leukocytes. A role is proposed for these peptides in the proliferation and maintenance of the middle ear submucosa during otitis media.

Acute Disease↗
PubMed1994

Hepatocyte growth factor/scatter factor has insulinotropic activity in human fetal pancreatic cells.

Fetal mesenchyme-derived factors are likely to play an important role in pancreatic islet development and growth. We have used primary cultures of human fetal pancreatic tissue to identify growth factors that have morphogenic, mitogenic, and insulinotropic activity. The formation of islet-like cell clusters (ICCs) during a 6-day culture was stimulated two- to threefold by hepatocyte growth factor/scatter factor (HGF/SF) basic fibroblast growth factor (FGF)-2, and to a lesser extent by keratinocyte growth factor (FGF-7) and insulin-like growth factor-II (IGF-II). In contrast, transforming growth factor-beta (TGF-beta) had a strong inhibitory effect. The ICCs formed during HGF/SF stimulation consisted mainly of epithelial cells, whereas FGF-2-induced ICCs were predominantly nonepithelial. Furthermore, although both FGF-2 and HGF/SF increased the total insulin content of the cultures, only HGF/SF increased the insulin content per DNA. Quantitatively, HGF/SF stimulated a 2.3-fold increase in the proportion of insulin-positive cells and a 3-fold higher number of replicating beta-cells. Blocking of the IGF-I receptor inhibited ICC formation but did not affect their insulin content. Immunoneutralizing TGF-beta resulted in increased cell growth and insulin content, indicating the presence of an endogenous inhibitory TGF-beta activity in the model system. Our results suggest that HGF/SF may be an important component of the fetal mesenchyme-derived factors responsible for pancreatic islet development. HGF/SF also may prove valuable for supporting the in vitro growth of islet cells.

Abortion, Legal↗
PubMed1993

Phosphorylation of basic fibroblast growth factor (FGF-2) in the nuclei of SK-Hep-1 cells.

The subcellular fractions containing protein kinases capable of phosphorylating basic fibroblast growth factor (FGF-2) are unknown, but having previously characterized one that is associated with the plasma membrane [1991, Mol. Endocrinol. 5, 1003-1012] we evaluated the catalytic properties of another in the nucleus. The reaction is time (linear up to 15 min), enzyme (2,000-25,000 nuclei/ml), and substrate (Km 0.18 microM) dependent, and the targets serine. DNase pretreatment of nuclei decreases the incorporation of phosphate into FGF-2 by 50% and the reaction. It is also inhibited by heparin (EC50 1 microgram/ml) and spermidine (EC50 3 microM). Calcium and cAMP have no effect. We conclude that the kinase is distinct from PKA, and PKC, and suggest that changes in glycosaminoglycan and polyamine concentrations during the cell cycle may modulate FGF-2 phosphorylation in the nucleus, or as it is translocated to the nucleus.

3T3 Cells↗
PubMed1993

Reducing the heterogeneity of chemically conjugated targeted toxins: homogeneous basic FGF-saporin.

Basic fibroblast growth factor-saporin (FGF-SAP) is an extremely potent cytotoxic agent for cells bearing the FGF receptor. For its synthesis, the two free cysteines on the surface of basic FGF are available for linking by disulfide bridge to SAP which has been derivatized with a reactive sulfhydryl. Because of the heterogeneous nature of the synthesis, the resulting conjugate is heterogeneous as judged by gel electrophoresis. We have removed by site-directed mutagenesis one of the reactive cysteines of basic FGF and have purified monoderivatized SAP to use as the reactants. The resulting chemical conjugate shows a single band containing only 1 mol of basic FGF and 1 mol of SAP per molecule. This homogeneous conjugate is a potent cytocidal agent to cells bearing the FGF receptor.

3T3 Cells↗
PubMed1993

Acidic and basic FGF mRNA expression in the adult and developing rat cochlea.

In situ hybridization was used to document the distribution of mRNA encoding acidic and basic fibroblast growth factor (aFGF and bFGF) in the rat cochlea from embryonic day (E) 16 to postnatal day (P) > 60. bFGF mRNA was not detected in the cochlea at any age. In the adult, aFGF mRNA was strongly expressed in spiral ganglion (SG) neurons, and this expression increased from base to apex. The stria vascularis (SV) and spiral prominence (SP) showed lesser expression which was equal in all turns. Developmentally, low level expression of aFGF mRNA was first seen in the SG at E-20, and remained low until P-4. Expression increased from P-6 to P-14, when adult levels were reached. aFGF mRNA was also observed in the developing hair cells of all turns at E-20. This expression increased after birth but disappeared after P-6. Expression in the SV and SP was first noted at E-20 and reached adult levels by P-16 and P-10, respectively. High levels of aFGF mRNA in the adult SG suggest that aFGF is important for the maintenance of SG neuron function and structure. aFGF in hair cells during the first postnatal week may be involved in the establishment of cochlear innervation.

Animals↗
PubMed1993

Direct application of basic fibroblast growth factor improves tympanic membrane perforation healing.

Topical application of basic fibroblast growth factor (b-FGF) on tympanic membrane (TM) perforations was studied in guinea pigs. One-millimeter simple round TM perforations or 2-mm TM perforations with medially flapped borders were performed. Either b-FGF or placebo was instilled in each ear on the day of surgery and daily thereafter. Treatment was applied either directly to the perforation or to a Gelfoam pledget over the defect. When no scaffolding material was interposed, b-FGF induced a faster healing response characterized by a hyperplastic but linear subepidermal connective tissue reaction compared to the control. When Gelfoam was interposed as a scaffold, a voluminous scar protruding into the middle ear cavity and involving the ossicles was observed in both b-FGF and control animals. Gelfoam-induced scars did not decrease after long-term observation, therefore discouraging its use.

Animals↗
PubMed1993

Growth factors during proliferation of the middle ear mucosa.

The presence of growth factors during otitis media with effusion (OME), induced by antigenic stimulation of the middle ear, was explored in guinea pigs. There was a significant increase in heparin-binding proliferative activity detected in mucosal tissue. This heparin-binding activity was identified as basic fibroblast growth factor (FGF) using several criteria. First, the majority of this activity was eluted from heparin-Sepharose gels with 1.3-1.8 M NaCl, consistent with basic FGF. Second, these fractions are potent stimulators of endothelial cell proliferation, characteristic of basic FGF. Third, the fractions contain basic FGF-like immunoreactivity based on radioimmunoassay. Finally, Western blotting of tissue extracts reveals the presence of an 18 kDa protein that is indistinguishable from basic FGF. We conclude that basic FGF plays a major role in the proliferation of the middle ear mucosa during OME.

Animals↗
PubMed1993

Characterization of a saporin mitotoxin specifically cytotoxic to cells bearing the granulocyte-macrophage colony-stimulating factor receptor.

When granulocyte-macrophage colony-stimulating factor (GM-CSF) is chemically conjugated to the ribosome-inactivating protein saporin, the resulting protein conjugate is highly toxic for cells expressing the GM-CSF receptor. Structural and Western blot analyses of the purified conjugate establish that it contains equimolar amounts of the starting materials and is free of any contamination by the non-conjugated components. The resulting bifunctional reagent is specifically cytotoxic to cells expressing the GM-CSF receptor, but is ineffective to cells that do not express the receptor. The cytotoxic activity is inhibited in a dose-dependent manner by GM-CSF, but not by any one of five other peptide growth factors. This is the first report of a mitotoxin for cells that express the GM-CSF receptor and which promises to be a valuable tool to study the expression of the GM-CSF receptor in normal and pathological states.

Animals↗
PubMed1992

Enhanced expression of transforming growth factor beta 1 in the rat brain after a localized cerebral injury.

It is becoming clear that transforming growth factor beta (TGF beta) may be a key factor regulating inflammatory and tissue specific wound responses. Because the formation of a glial-collagen scar at CNS lesion sites is thought to contribute to the pathology associated with penetrating CNS injuries, and because in the periphery TGF beta 1 stimulates fibroblast deposition of scar tissue, we used in situ hybridization and immunohistochemistry to investigate the effect of a defined cerebral lesion on the local expression of TGF beta 1. Induction of TGF beta 1 mRNA and protein is relatively diffuse in the neuropile around the margins of the lesion at 1, 2 and 3 days, but becomes localized to the region of the glial scar at 7 and 14 days. The signal intensity for TGF beta 1 mRNA and protein is maximal between 2 and 3 days and decreases between 7 and 14 days after lesion. The predominant cell types in the neuropile localizing TGF beta 1 mRNA and protein have the morphological characteristics of astrocytes, although macrophages are also detected. An induction of TGF beta 1 mRNA was also observed in endothelial cells of the meninges, hippocampal fissure and choroid plexus, at 2 and 3 days. However, this is dramatically reduced by 7 days and has disappeared by 14 days. These results suggest a role for TGF beta 1, not only in inflammation, but also in the tissue-specific glial scar formation that occurs in the CNS. Furthermore, they suggest a potential therapeutic use of TGF beta 1 antagonists in the CNS to help limit the pathogenesis associated with matrix deposition in the wound.

Animals↗
PubMed1992

Elimination of smooth muscle cells in experimental restenosis: targeting of fibroblast growth factor receptors.

Factors in plasma and platelets do not fully account for the proliferation of smooth muscle cells in vascular injury, implying that additional factors are involved. Recently, we and others have observed that vascular injury regulates basic fibroblast growth factor, suggesting a further role for this pleiotropic factor. We report here that injury of rat arteries leads to an increase in fibroblast growth factor receptors in vascular smooth muscle cells. This up-regulation makes smooth muscle cells susceptible, in vitro and in vivo, to the lethal effects of a conjugate of basic fibroblast growth factor with the ribosome inactivator saporin. Saporin alone has no effect, whereas the conjugate kills proliferating, but not quiescent, smooth muscle cells in vitro. In vivo, one to three doses inhibit neointimal proliferation but have no apparent effect on the uninjured artery. Thus, the up-regulation of fibroblast growth factor receptors in vascular injury suggests new therapeutic possibilities for such refractory conditions as restenosis following balloon angioplasty.

Amino Acid Sequence↗
PubMed1992

Antitumor activity of basic fibroblast growth factor-saporin mitotoxin in vitro and in vivo.

Many cancer cell lines express basic fibroblast growth factor (FGF) receptors, making them potential targets for the delivery of FGF-based cytotoxic compounds. To this end, we have investigated the antitumor activity of a novel mitotoxin, Fibroblast Growth Factor-saporin (FGF-SAP), a conjugate of FGF and the ribosome-inactivating protein, saporin. In vitro, FGF-SAP is cytotoxic for human melanoma, teratocarcinoma, and neuroblastoma cells expressing FGF-receptors. Mice treated with FGF-SAP i.v., on a variety of schedules, showed dramatic tumor growth inhibition with minimal toxicity. Thus, FGF-SAP appears to be a well-tolerated and potent antitumor agent. The potential of FGF-targeted cytotoxicity is discussed.

Animals↗
PubMed1992

Biphasic effect of the mitotoxin bFGF-saporin on bovine lens epithelial cell growth: effect of cell density and extracellular matrix.

We have studied the effect of a specific FGF receptor suicide antagonist on the growth of bovine epithelial cells (BEL cells) in culture. This basic fibroblast growth factor-saporin conjugate (bFGF-SAP) has a biphasic effect on bovine lens epithelial cells (BEL cells). Whereas 0.01 nM and 0.1 nM bFGF-SAP stimulate BEL cells proliferation, 1 nM and 10 nM bFGF-SAP have the predicted toxic effects on BEL cell growth. The toxicity of bFGF-SAP is observed 2 to 3 days after the initial treatment and depends on cell density. Accordingly, the sensitivity of confluent cells to bFGF-SAP is reduced compared to sparse cells. A time course analysis reveals that bFGF-SAP is effective after a short exposure to cells and that its effects are not increased with longer treatments. Cell growth on bFGF-SAP pretreated extracellular matrix (ECM) or posterior lens capsule (PLC) is also affected. Basic FGF-SAP has been shown to bind to the extracellular material, allowing a modulation of lens cells migration and survival by a single treatment in vitro. This finding raises the possibility of its use in vivo to prevent capsules invasion by lens cells after cataract surgery.

Animals↗
PubMed1992

Basic fibroblast growth factor in cells derived from Dupuytren's contracture: synthesis, presence, and implications for treatment of the disease.

Dupuytren's contracture (DC) is associated with fibroblast and endothelial cell proliferation. We have identified a fibroblast and endothelial cell mitogen, basic fibroblast growth factor (FGF), in cells derived from this tissue and characterized the effects of this growth factor on DC cells. Northern blot analysis of DC cells reveals the presence of basic FGF mRNA species, and the DC cells coexpress multiple forms of basic FGF. Radioreceptor assays establish that the DC cells have high-affinity binding sites for basic FGF and proliferate in response to exogenous recombinant basic FGF. Furthermore, a conjugate between saporin (a ribosome-inactivating protein) and basic FGF, which is cytotoxic to cells possessing the basic FGF receptor, is also cytotoxic to DC cells. The possibility that basic FGF-saporin could be a potential therapeutic agent for prevention of recurrence of the disease after surgery is discussed.

Cell Division↗